Lightroom: Slideshows do not work at all. I get nothing but a black screen. On two different computers.

There is a bug that has been haunting me ever since Lightroom 4. This affects me on both my computers, one is a Mac Pro tower, the other a MacBook Pro, both running Mountain Lion. I have scoured the net and haven't been able to find anyone else who has this bug, yet I get it on both my computers.

Whenever an image is being presented in the slideshow, it will fade in as it is supposed to, but the instant the transition is finished the screen goes black. Then the next image fades in and as soon as the fade is complete, black again. And so on.

I have tried every combination I can think of with the settings on the right panel including shutting all the unnecessary stuff off and this still happens. If I shut off the transition altogether all I see is a black screen. Basically I can the image during transition, but when it's supposed to be holding the image all I get is a blank screen.

It will also do this when I try to preview a slideshow. However, if I export a slideshow as a movie file the movie file does not exhibit this problem and the contents appear to be correct.

This happens to me in the exact same way on both my computers, yet after searching the web for hours I haven't been able to find any other mention of a similar problem.

On a Mac the video drivers are packaged in the OS, updating them separately is not an option and I'm running the latest Mac OS and therefore the latest video drivers. Also I'm running on two different computers, one with nVidia video hardware and one with ATI so it's not likely a video driver problem.